Rotation unit, rock drilling unit and method for rock drilling

ABSTRACT

A rotation unit, rock drilling unit and method for rock drilling. The rotation unit includes a main shaft that is rotated around its longitudinal axis by means of a rotating motor. The main shaft is supported on a body of the rotation device slidingly in the axial direction. This slide property is utilized when connection threads of drilling equipment and drilling components comprised by it are connected.

BACKGROUND OF THE INVENTION

The invention relates to a rotation unit for rock drilling, which rotation unit has no percussion device. The purpose of the rotation unit is to generate the required rotation for drilling equipment to be connected thereto, at the outermost end of which equipment there is a drill bit for breaking rock.

Further, the invention relates to a drilling unit and a method for rock drilling. The field of the invention is described in more detail in the preambles of the independent claims of the application.

Holes can be drilled in rock by means of various rock drilling machines. Drilling may be performed with a method combining percussions and rotation (percussive drilling), or drilling may be based on mere rotation without a percussive function (rotary drilling). Further, percussive drilling may be classified according to whether the percussion device is outside the drill hole or in the drill hole during the drilling. When the percussion device is outside the drill hole, the drilling is usually called top hammer drilling, and when the percussion device is in the drill hole, the drilling is typically called down-the-hole drilling (DTH). In a top hammer drilling machine, the percussion device and the rotation device are combined into one entity, whereas in a rotary drilling machine and DTH drilling machine, there is a rotation unit which is completely without a percussion device. This application is specifically directed to such a rotation unit without a percussion device and to the use thereof.

The rotation unit comprises a main shaft that is rotated around its longitudinal axis. Rotation force is generated by a rotating motor connected to the main shaft through a gear system. As the drilling progresses, more drilling tubes are connected to the drilling equipment and, correspondingly, disconnected after the drill hole has been finished and it is time to start drilling a new drill hole. The drilling tubes are provided with connection threads, due to which they require what is called a floating spindle that allows the threads to be screwed and unscrewed without simultaneous accurate control of the feeding movement. The floating spindle enables the required axial movement that results from the pitch of the connection threads. Floating spindles used nowadays are separate units which are connected to a rotation unit before the first drilling tube. Such separate floating spindle units have, however, turned out to cause problems to the durability of the equipment.

BRIEF DESCRIPTION OF THE INVENTION

It is an object of this invention to provide a novel and improved rotation unit, rock drilling unit and method for rock drilling.

The rotation unit according to the invention is characterized in that the main shaft is supported to the body slidingly in the axial direction.

The rock drilling unit according to the invention is characterized in that the main shaft of the rotation device is supported to the body slidingly in the axial direction.

The method according to the invention is characterized by allowing the main shaft of the rotation unit to move axially in relation to the body of the rotation unit when the drilling equipment and components of the drilling equipment are connected and disconnected.

The idea is that the main shaft of the rotation unit is bearing-mounted on the body in such a way that it can slide an allowed, predetermined axial length of movement in relation to the body.

Thus, an advantage is that the axial movement of the main shaft allows the connection threads of the drilling equipment to be unscrewed and screwed without there being a need to arrange any separate floating spindle unit in the drilling equipment. Arranging a slide property in the rotation unit allows the structure to be more firm and durable than before.

The idea of an embodiment is that the main shaft is supported to the body in the radial direction in the portion of the front end by means of a front bearing, and in the portion of the rear end by means of an end bearing. Both bearings are slide bearings and may be of a suitable slide bearing metal, for example. The structure allows the axial distance between the bearings to be arranged relatively long. Owing to this, the crosswise forces transmitted from the drilling equipment to the main shaft during drilling can be received well to the firm body of the rotation unit. Further, the durability of the structure is improved by the opportunity to arrange the front and end bearings in oil-lubricated spaces.

The idea of an embodiment is that the main shaft is bearing-mounted on the body by means of a front bearing and an end bearing, the axial distance between these being great in relation to the diameter of the main shaft. The bearings have an axial bearing distance, and the main shaft has bearing diameters at the point of the bearings. According to observations, the bearing of the main shaft is particularly firm when the ratio of the bearing distance to the greatest one of the bearing diameters is at least 3:1. The bearing diameters may be equal or unequal at the front and end bearings. The bearing distance is the dimension between the functional middle points of the front and end bearings.

The idea of an embodiment is that the transmission members between the gear system and the main shaft comprise sliding members which allow axial movement of the main shaft without any axial forces being transmitted to the gear system. When there are no axial loads directed from the main shaft to the gear system or the rotating motor, the durability of the rotation unit is good.

The idea of an embodiment is that rotation force is transmitted to the main shaft from the portion of its rear end. There is more space for the transmission members at the rear end of the main shaft, whereby they can be dimensioned and positioned more freely than in solutions where rotation force is transmitted from the portion of the front end of the main shaft.

The idea of an embodiment is that the rotating motor and the gear system are positioned as an extension of the rear end of the main shaft. The rotating motor, gear system and main shaft are then positioned successively on the same axial line. Thus, the rotation unit, seen in the lateral direction, may be rather narrow. Although the length increases on the side of the rear end of the rotation unit, this has not turned out to do any harm to the structure or operation. Further, the rotating motor and gear system may be modules which can be easily and quickly detached and replaced with a new one without having to disassemble the rest of the rotation unit structure. There is plenty of space for handling the modules at the rear end of the rotation unit. It is also feasible to provide the rear end of the rotation unit with modules having different powers and other properties if it is desirable to affect the properties of the rotation unit.

The idea of an embodiment is that the outer periphery of the main shaft has at least one arranged to transmit axial feed force between the body and the main shaft. The feed flange has axial support surfaces which participate in transmitting axial forces. Further, the body has a sliding space at the location of the feed flange. The sliding space is an elongated annular space around the main shaft, having ends that define the sliding space in the axial direction. The front end and the rear end comprise support surfaces which may participate in transmitting axial forces.

The idea of an embodiment is that the feed flange and the sliding space at the location thereof are positioned in the portion of the front end of the main shaft. Then, axial forces are transmitted between the main shaft and the body as close to the front end of the rotation unit and the drilling equipment as possible. The axial forces do thus not stress the rear part of the main shaft or the components of the rotation unit that are positioned in the rear part. These aspects are also preferable with regard to the durability of the rotation unit.

The idea of an embodiment is that the feed flange is positioned in the sliding space on the front side of the front bearing supporting the main shaft. Thus, the front bearing transmits axial forces between the feed flange and the rear end of the sliding space when the feed is towards the drilling direction. The front bearing serves as a radial bearing of the main shaft and as an axial bearing. The front bearing is a slide bearing that is extremely capable of receiving great axial forces during drilling. The front bearing may be arranged in the sliding space slidingly in the axial direction, whereby it may be arranged to move together with the main shaft. Further, the sliding space may be oil-lubricated, which improves the durability of the front bearing even more.

The idea of an embodiment is that the structure of the rotation unit comprises an axial damper. The axial damper is thus integrated to form a part of the rotation unit. The axial damper may be used for damping vibration, impacts, shock waves and other axial stresses which affect the main shaft and are transmitted to the main shaft from the drilling equipment. Such an axial damper significantly reduces vibration and stress waves directed to the body and body parts from the drilling equipment through the main shaft, whereby less stress is directed to the components behind the axial damper. Further, the axial damper may also reduce stresses directed the components on the front side of the damper, i.e. on the side of the drilling equipment, at least to some extent.

The idea of an embodiment is that the axial damper comprises at least one end damper arranged at the end of the sliding space. The axial damper may comprise a rear end damper doing the damping in the drilling direction, and a front end damper doing the damping in the return direction. In some cases, the damper may comprise only a rear end damper. The advantage of an end damper is that its structure is simple and that it is inexpensive and requires little maintenance.

The idea of an embodiment is that the end damper is an annular piece made of a compressive elastic material. The end damper may be of a polymer material, such as suitable polyurethane. Such dampers have turned out resist-wear surprisingly well.

The idea of an embodiment is that the axial damper comprises at least one pressure-medium-operated damper element. Such an axial damper may have working pressure spaces into which pressure medium, such as hydraulic fluid, may be conducted which affects the working pressure surfaces in the working pressure spaces. It is further feasible for the axial damper to comprise one or more damping pistons arranged to affect the main shaft in the axial direction either directly or by means of appropriate intermediate pieces. The pressure of the pressure medium may be directed to the damping pistons to generate desired damping in the extreme positions of the sliding movement of the main shaft.

The idea of an embodiment is that there are connecting members at the front end of the main shaft of the rotation unit for rigid mounting in the axial direction. Thus, the drilling equipment is mounted on the main shaft without any axially directed sliding connection. The connecting members may comprise connection threads to which the drilling tube, an adapter piece or the like component can be attached. This embodiment reduces the loads directed to the connection between the main shaft and the drilling equipment.

The idea of an embodiment is that the outer periphery of the rear end of the main shaft comprises an axial set of grooves for transmitting rotation force. Further, around the rear end of the main shaft, there is a rotating sleeve the inner periphery of which comprises a corresponding axial set of grooves. Thus, between the outer surface of the rear end of the main shaft and the inner surface of the rotating sleeve, there is transmission connection allowing axial movement of the main shaft. The rotating sleeve is bearing-mounted on the body with axial bearings, whereby no axial forces are transmitted from the main shaft to the gear system through the transmission members. These features are preferable:with regard to the durability of the structure.

The idea of an embodiment is that the gear system is a planetary gear. The planetary gear may be physically rather small and also short in the axial direction, whereby it is easy to arrange at the rear end of the main shaft.

The idea of an embodiment is that the main shaft comprises a first main shaft part and a second main shaft part arranged on the same axial line and connected to each other. The connection between the main shaft parts is axially rigid. On the outer periphery of the rear end of the first main shaft part, there is a set of grooves by means of which rotation force can be transmitted to the main shaft. The front end of the second main shaft part, in turn, comprises a connection thread for attaching the drilling equipment. The main shaft is bearing-mounted on the body by means of the front bearing and end bearing of the first main shaft part only. The bearings are arranged at as great an axial distance from each other as possible, whereby they receive the crosswise loads well. Further, the feed flange may be arranged as a fixed part of the second main shaft part. Alternatively, the feed flange may be a separate piece, for example an annular flange, which is arranged between the main shaft parts.

The idea of an embodiment is that the portion between the front bearing and the end bearing comprises a pressure medium space surrounding the main shaft and in connection with a feed channel for pressurized air or the like pressure medium. The main shaft has one or more channels for conducting pressure medium from the pressure space into a centre channel in the main shaft and further along it to the drilling equipment to be connected to the main shaft. The pressure space around the main shaft may be isolated from the bearing spaces with shaft seals. Then, the pressure medium remains separate from the lubrication oil of the bearing spaces.

The idea of an embodiment is that the rock drilling unit comprises a carriage which is moved on a feed beam by means of a feed device. The body of the rotation unit is immovably attached to the carriage. Thus, the rotation unit and its body always move along with the carriage, there being no slidingly arranged body parts in the rotation unit.

The idea of an embodiment is that the rotation unit is intended for rotary drilling, in which drilling takes place by the effect of mere rotation and feed force without any percussion device.

The idea of an embodiment is that the rotation unit is intended for DTH drilling, in which the rotation unit and the percussion device are in opposite end portions of the drilling equipment. Hence, there is no percussion device in the rotation unit but it is in connection with the drilling equipment. The drill bit is typically attached directly to the percussion device.

The idea of an embodiment is that the axial position of the main shaft is monitored, and this information may be transmitted to a control unit that controls the handling device for drilling tubes in the rock drilling unit. Further, the information on the position of the main shaft may be utilized in controlling the screwing and unscrewing of the threads. The position of the main shaft may be monitored by means of one or more sensors or measuring devices.

The idea of an embodiment is that the axial position of the main shaft is monitored, and this position information is used as an aid in controlling the feed force during the drilling.

The idea of an embodiment is that the rotation unit comprises at least one axial damper as well as means for monitoring the axial position of the main shaft. The position information on the main shaft may be used for monitoring the condition of the axial damper. The control unit may comprise a control strategy for condition monitoring. The axial damper may comprise one or more damper elements made of a compressible material and having a planned functional compression area, for instance 10%. By means of the position information, it can be observed if this planned compression is exceeded, for example in cases where the damper element has permanently lost its elasticity and resilience or has been damaged in another way. Owing to this embodiment, damage of the axial damper can be observed in time.

The idea of an embodiment is that the main shaft is one integral shaft piece. The feed flange may be an integral undetachable part of the main shaft. Alternatively, the feed flange may be a piece formed separately, for example a ring -flange, which may be immovably attached to the shaft piece.

The idea of an embodiment is that the rotating motor is a hydraulic motor.

The idea of an embodiment is that the rotating motor is an electric motor.

The idea of an embodiment is that the rotation unit does not comprise- a gear system at all,but rotation force is transmitted to the main shaft by means of other transmission members. The rotation speed and torque of the rotating motor can be controlled in a versatile and accurate manner. The rotating motor is of the type called a direct drive motor. Motors of this type are available as hydraulically operated and electrically operated motors. As the gear system can be left out of the rotation unit, there are fewer components to be maintained and subject to damage. Further, the rotation unit can be made smaller.

The idea of an embodiment is that the transmission members are provided with members for promoting the flowing of lubrication oil in the lubrication space. Thus, a rotating hub or a rotating sleeve, for example, may be provided with screw-like members which generate a flow of lubrication oil by the effect of the rotating movement. In this way, durability of transmission surfaces, transmission components and bearings can be improved.

BRIEF DESCRIPTION OF THE FIGURES

Some embodiments of the invention will be explained in greater detail in the attached drawings, in which

FIG. 1 shows schematically a rock drilling rig provided with a rotation unit for rotating drilling equipment around its longitudinal axis;

FIG. 2 shows schematically the principle of DTH drilling and the operation of a rotation unit in it;

FIG. 3 shows schematically and greatly simplified the principle of a rotation unit in accordance with the invention;

FIGS. 4 and 5 show schematically a partially cross-sectional top view of a second rotation unit in accordance with the invention in two different axial extreme positions of the main shaft.

FIG. 6 shows schematically a top view of yet another rotation unit in which the main shaft is an integral piece and rotated by a direct drive motor.

In the figures, some embodiments of the invention are shown simplified for the sake of clarity. Like reference numerals-refer to like parts in the figures.

DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION

FIG. 1 shows a rock drilling rig 1 that comprises a movable carrier 2 provided with a drilling boom 3. The boom 3 is provided, with a rock drilling unit 4 comprising a feed beam 5, a feed device 6 and a rotation unit 7. The rotation unit 7 may be supported to a carriage 8, or alternatively the rotation unit may comprise sliding parts or the like support members with which it is movably supported to the feed beam 5. The rotation unit 7 may be provided with drilling equipment 9 which may comprise one or more drilling tubes 10 connected to each other, and a drill bit 11 at the outermost end of the drilling equipment. The drilling unit 4 of FIG. 1 is intended for rotary drilling in which the rotation unit 7 is used for rotating the drilling equipment 9 around its longitudinal axis in direction R and, at the same, the rotation unit 7 and the drilling equipment 9 connected to it are fed with feed force F by means of the feed device 6 in drilling direction A. Thus, the drill bit breaks rock due to the effect of rotation R and feed force F, and a drill hole 12 is formed. When the drill hole 12 has been drilled to a desired depth, the drilling equipment 9 can be pulled by means of the feed device 6 out of the drill hole 12 in return direction B, and the drilling equipment can be disassembled by unscrewing connection threads between the drilling tubes 10 by means of the rotation unit 7. The main shaft of the rotation unit 7 is provided with a sliding function for screwing and unscrewing connection threads of the drilling equipment.

FIG. 2 shows a second drilling unit 4, which differs from the one in FIG. 1 in such a way that the drilling equipment 9 is provided with a percussion device 13. The percussion device 13 is thus at the opposite end of the drilling equipment 9 in relation to the rotation unit 7. During drilling, the percussion device 13 is in the drill hole, and the drill bit 11 may be connected directly to the percussion device 13. The rotation unit 7 may consist of modules, whereby it may have a basic module 14 with a main shaft and its sliding support, as well as a gear system module 15 and a rotating motor module 16. The modules may be arranged successively on the same axial line.

FIG. 3 shows one possible embodiment of the rotation unit 7 in a highly simplified manner. The rotation unit 7 comprises a main shaft 17, the front end of which comprises connection threads 18 for attaching the drilling equipment 9. In the portion of the opposite end of the main shaft 17, there may be an axial set of grooves 19, to which rotation force is transmitted through a rotating sleeve 20. The rotating sleeve 20 has a corresponding axial set of grooves, whereby the main shaft 17 can slide in the axial direction in relation to the rotating sleeve 20. The rotating sleeve 20 may be bearing-mounted to be immovable in the axial direction. Rotation force can be transmitted to the rotating sleeve 20 from one or more gear systems 15 which are connected to the rotating motor 16. As shown in the figure, it is possible to transmit rotation force from a plurality of gear systems 15 to the main shaft. Then, the gear systems 15 may be arranged on opposite sides of the main shaft 17 to eliminate crosswise loading.

It is seen in FIG. 3 that the main shaft 17 can be bearing-mounted with an end bearing 21 and a front bearing 22. The bearings 21, 22 are slide bearings, whereby they allow axial movement S of the main shaft 17. The bearings 21, 22 are arranged at a great axial bearing distance L from each other, whereby the bearings 21, 22 are well capable of receiving crosswise loads directed to the main shaft. The bearings 21, 22 positioned far from each other make good support for the main shaft. At the bearing points, the main shaft has diameters D1 and D2 which may, depending on the embodiment, be either equal or somewhat unequal. The ratio of the bearing distance L between the bearing points to the greater one of these diameters D1, D2 is at least 3:1. The bearing point refers to the functional middle point of the bearing.

FIG. 3 further shows support surfaces on which feed force F is transmitted from a body 23 of the rotation device 7 to the main shaft 17. The main shaft 17 may comprise one or more shoulders, flanges or the like form surfaces with a support surface 24 a for transmitting feed force in drilling direction A, and a support surface 24 b for transmitting feed force in return direction B. The body 23 has corresponding support surfaces 25 a and 25 b. Around the main shaft 17, there may be a sliding space 26 at the point of said support surfaces. The axial end surfaces of the sliding space 26 may serve as support surfaces 25 a and 25 b.

The pressure medium, such as pressurized air, may be fed along a pressure channel 27 to the main shaft 17 and further to the drilling equipment.

FIG. 4 shows a second rotation device 17 in which some of the features correspond to those shown in FIG. 3. In the solution shown in FIG. 4, the main shaft 17 comprises a first main shaft part 17 a on the side of the rear end, and a second main shaft part 17 b on the side of the front end, which are connected to each other with axially rigid connection 28, for example with a connection thread. The second main shaft part 17 b may comprise a feed flange 29 the axial surfaces of which form support surfaces 24 a, 24 b. Around the feed flange 29, there is a sliding surface 26, which is an annular space defined in the axial direction by ends 25 a and 25 b also serving as support surfaces 25 a, 25 b in the body 23. The front bearing 22 is a slide bearing, and it is arranged in the sliding surface 26 on the side of the rear surface of the feed flange 29. The front bearing 22 may slide in the:sliding Space 26 along with the main shaft 17. When the feed takes place in drilling direction A, feed force is transmitted from the body 23 through the end 25a and front bearing 22 to the feed flange 29 and further to the main shaft 17. When the feed takes place in return direction B, feed force is transmitted from the body 23 through the end 25 b and feed flange 29 to the main shaft 17. The sliding space 26 may comprise an end damper 30, 31 either at one end or at both ends. The end damper 30, 31 may be an annular piece comprising elastic compressive material. The end damper enables damping of impacts and stresses transmitted from the drilling equipment 9 to the main shaft 17 and further to the rest of the structure. In some cases, there are no end dampers 30 and 31, or alternatively, only a rear end damper 30 is used. The sliding space 26 may be provided with lubrication oil from a channel 32, whereby the front bearing 22, end dampers and support surfaces are oil-lubricated.

Around the main shaft 17, there may be a pressure medium space 33, into which pressurized air or the like can be fed from the channel 27. The main shaft 17 comprises channels for conducting pressure medium to its front end and further to the drilling equipment 9. The pressure medium space 33 may be separated with axial seals 35 and 36 from the sliding space 26 and from a lubrication space 37 at the end bearing 21. The space 37 may be provided with lubricant from a channel 38, whereby also the end bearing 21 is oil-lubricated.

On the outer periphery of the rear end of the first main shaft part 17 a, there is a set of grooves 19 to which a rotating sleeve 20 is connected, having a corresponding set of grooves. The set of grooves allows movement of the main shaft 17 in the axial direction. The rotating sleeve 20 is supported to the body 23 by bearings 39 and 40 in such a way that it is immovable in the axial direction. Rotation force can be transmitted to the rotating sleeve 20 by means of a rotating hub 41 connected to a shaft 42 or the like of the gear system 15. Of course, it may be feasible to combine the structure of the rotating sleeve 20 and rotating hub 41 into one entity. The gear system 15 and rotating motor 16 may be module-structured, and they may be arranged on an axial extension of the main shaft 17.

FIG. 5 shows a situation where the main shaft 17 has moved into its extreme front position in the axial direction. This sliding movement may take place for instance while the connection threads are connected.

The embodiment shown in FIG. 6 deviates from the one shown in FIGS. 4 and 5 in such a way that the main shaft 17 has not been formed of two pieces but it is one integral shaft-like piece. The feed flange 29 may be an integral part of the main shaft 17, or it may be a piece manufactured separately and attached to the shaft part of the main shaft. In FIG. 6, a broken line indicates the connection between the feed flange and the shaft part, which may be a welded joint, for example. Further, the rotation unit 7 of FIG. 6 deviates in such a way that it has no gear system but the rotating motor 16 is connected to a rotating hub 41 by means of a shaft 42 or another transmission component. The rotating motor may be a direct drive motor dimensioned in such a way that no separate gear system is needed.

It is seen in FIG. 6 that the axial position of the main shaft 17 may be monitored by means of one or more sensors 50. The sensor 50 may be arranged at a suitable location in the structure of the rotation unit 7. Instead of the sensor 50, a suitable measuring device can be used. Identification information may be transmitted by means of a wireless or wire data transmission connection 51 to a control unit 52 which may take the identification information into account in controlling the actuators comprised by the rock drilling unit. Further, the position information may be used for controlling the feed force of the drilling and monitoring the condition of the axial damper.

FIG. 6 further shows flow members 49 the purpose of which is to generate flow of lubrication oil in the lubrication space and thus to improve lubrication of the components in the lubrication space. For instance a thread, a spiral or projections on the outer periphery of the rotating hub 41 may serve as the flow member 49.

FIG. 6 shows yet another alternative embodiment where the main shaft 17 is supported to the body 23 or a body part in quite the front part thereof with a radial bearing 53 shown by a broken line and greatly simplified. Thus, the bearing distance L between the bearings 21 and 53 can be made great. Further, in this embodiment, the bearing 22 may be an axial bearing which does not have to participate in radial supporting of the main shaft 17 at all. There may be clearances between the bearing 22 end the main shaft 17 and between the bearing 22 and the sliding space 26 in such a way that the bearing 22 easily moves axially. This property may be preferable with regard to damping axial stress waves. This embodiment may be also utilized more generally in the rotation unit 7 provided with an integrated axial damper. The solution is thus not confined to the exact embodiment of FIG. 6.

It should be noted that in the above embodiments the rotating motor may a hydraulic motor or an electric motor. Further, a direct drive motor may also be used in the rotation units 7 shown in FIGS. 3 to 5, in which case, deviating from the solutions of the figures, they have no gear system.

in some cases, features disclosed in this application may be used as such, regardless of other features. On the other hand, when necessary, features disclosed in this application may be combined in order to provide varioust combinations.

The drawings and the related description are only intended to illustrate the idea of the invention. Details of the invention may vary within the scope of the claims. 

1. A rotation unit for rock drilling comprising: a body; a main shaft of an elongated piece having a front end with connection means for attaching drilling equipment and an opposite rear end, supported in the body and having at least two bearings rotatable in relation to its longitudinal axis, wherein an outer periphery of the main shaft includes at least one feed flange having axial support surfaces, the body including, at the location of the feed flange, an annular sliding space surrounding the main shaft and having an axial length, wherein the sliding space is defined by an axial front end and a rear end having support surfaces, the support surfaces of the feed flange and sliding space being arranged to transmit axial forces between the body and the main shaft, wherein the feed flange and the sliding space are positioned at the front end of the main shaft; a rotating motor; transmission members for transmitting rotation force from the rotating motor to the main shaft; axial support surfaces for transmitting axial forces between the body and the main shaft in a drilling direction and a return direction; channels for conducting a pressure medium to the main shaft and to the drilling equipment, wherein the main shaft is slidably supported on the body in an axial direction; and a front bearing disposed around the front end of the main shaft in the sliding space, the front bearing being positioned in a portion between the feed flange and the rear end of the sliding space,wherein the front bearing is a slide bearing slidably arranged in the sliding space in the axial direction.
 2. A rotation unit as claimed in claim 1, wherein the main shaft is supported in the body in a radial direction by a front bearing in the portion of the front end and by an end bearing in the portion of the rear end, wherein the front bearing and the end bearing are slide bearings.
 3. A rotation unit as claimed in claim 1, wherein the transmission members comprise sliding members which allow axial movement of the main shaft without transmitting axial forces.
 4. A rotation unit as claimed in claim 1, wherein a rotation force is transmitted to the main shaft from the portion of the rear end.
 5. A rotation unit as claimed in claim 1, wherein the rotating motor is positioned on the side of the rear end of the main shaft, wherein the rotating motor and the main shaft are arranged on the same axial line.
 6. (canceled)
 7. (canceled)
 8. A rotation unit as claimed in claim claim 1, further comprising an axial damper integrated with the rotation unit for damping axial stresses affecting the main shaft, the axial damper comprising at least one end damper arranged at the axial end of the sliding space.
 9. A rotation unit as claimed in claim 8, wherein the end damper made of a compressive elastic material.
 10. A rotation unit as claimed in claim 1, wherein the connection means disposed at the front end of the main shaft is a connection thread, whereby the connection between the rotation unit and the drilling equipment is rigid in the axial direction.
 11. A rotation unit as claimed in claim 1, wherein the main shaft has a first main shaft part and a second main shaft part arranged on the same axial line and connected to each other with an axially rigid connection, the outer periphery of the rear end of the first main shaft part having a set of grooves for transmitting rotation force, the first main shaft part being bearing-mounted on the body by the ends thereof by a front bearing (22) and an end bearing, and the front end of the second main shaft part including a connection thread for attaching the drilling equipment.
 12. A rotation unit as claimed in claim 1, wherein the main shaft is bearing-mounted on the body by a front bearing and an end bearing which have an axial bearing distance (L) and at the point of the bearings the main shaft has a first and second diameter, the ratio of the bearing distance to the greater one of the first or second diameter being at least 3:1.
 13. A rock drilling unit comprising: a rotation unit having a rotating motor for generating rotation force, a main shaft to which rotation force is transmitted by means of transmission members, and connection members for attaching drilling equipment to the main shaft, the rotation unit having a body and a a main shaft of an elongated piece having a front end with connection means for attaching drilling equipment and an opposite rear end supported in the body and having at least two bearings rotatable in relation to its longitudinal axis, wherein an outer periphery of the main shaft includes at least one feed flange having axial support surfaces, the body including, at the location of the feed flange, an annular sliding space surrounding the main shaft and having an axial length, wherein the sliding space is defined by an axial front end and a rear end having support surfaces, the support surfaces of the feed flange and sliding space being arranged to transmit axial forces between the body and the main shaft, wherein the feed flange and the sliding space are positioned at the front end of the main shaft and a front bearing is disposed around the front end of the main shaft in the sliding space, the front bearing being positioned in a portion between the feed flange and the rear end of the sliding space,wherein the front bearing is a slide bearing slidably arranged in the sliding space in the axial direction a feed beam by the support of which the rotation unit is movable in a drilling direction and a return direction; a feed device for generating feed forces; and drilling equipment including at least one drilling tube, a first end connected to the rotation unit for transmitting the feed forces and rotation forces to the drilling equipment, and a free end having a drill bit for breaking rock.
 14. A rock drilling unit as claimed in claim 13, further comprising a percussion device arranged in the portion of the free end of the drilling equipment, wherein the drill bit is connected to the percussion device.
 15. A rock drilling unit as claimed in claim 13, further comprising a carriage which is movable on the feed beam, wherein the body of the rotation unit is immovably attached to the carriage.
 16. A rock drilling unit as claimed in claim 13, further comprising at least one sensor for determining the axial position of the main shaft of the rotation unit.
 17. A method for drilling rock, comprising the steps of: drilling rock with a rock drilling unit which comprises at least a rotation unit, a feed beam, a feed device and drilling equipment; rotating a main shaft of the rotation unit around its longitudinal axis and transmitting rotational motion to the drilling equipment connected to the main shaft, the outermost end of which drilling equipment includes a drill bit for breaking rock; feeding the rotation device by the feed device, supported by the feed beam, in a drilling direction and a return direction; connecting the drilling equipment to the main shaft by a connection thread and connecting drilling components of the drilling equipment to each other with connection threads disposed between them; and allowing the main shaft of the rotation unit to move axially in relation to a body of the rotation unit when the drilling equipment and components of the drilling equipment are connected and disconnected. 